Thermoplastic elastomers based upon chlorinated polyethylene and a crystalline olefin polymer

ABSTRACT

Thermoplastic vulcanizates are prepared by curing, at least partially by dynamic vulcanization, blends of chlorinated polyethylene and crystalline thermoplastic polymers such as polypropylene. Inclusion of a plasticizing material or extender oil, e.g. trioctyl trimellitate, enhances softness and oil resistance of the blends. Vulcanizing materials include a basic material, normally added with the chlorinated polyethylene, and (1) a derivative of 2,5-dimercapto-1,3, 4-thiadiazole or (2) a combination of 2,5-dimercapto-1,3,4-thiadiazole and an activator material such as an amine having a boiling point of 110° C. or higher and a pk value less than 4.5.

BACKGROUND OF THE INVENTION

The present invention generally concerns thermoplastic elastomercompositions comprising blends of chlorinated polyethylene and acrystalline olefin polymer. The present invention also concernspreparation of said compositions by dynamic vulcanization or by asequential combination of dynamic vulcanization and static curing.Static curing may occur, for example in a heated oven. The presentinvention further concerns the use of a non-peroxide cure package toaccomplish said dynamic vulcanization.

Thermoplastic elastomers, which can be processed and fabricated bymethods used for thermoplastics and do not require vulcanization todevelop elastomeric properties, are known (see, for example, U.S. Pat.No. 3,265,765 as well as Hartman et al., "Butyl Grafted to PolyethyleneYields Thermoplastic Elastomer," Rubber World, October 1970, pp. 59-64).

Dynamic vulcanization is a process whereby a blend of plastic, rubberand rubber curative is masticated while curing the rubber. The term"dynamic" indicates the mixture is subjected to shear forces during thevulcanization step as contrasted with "static" vulcanization wherein thevulcanizable composition is immobile (in fixed relative space) duringvulcanization. One advantage of dynamic vulcanization is thatelastoplastic (thermoplastic elastomeric) compositions may be obtainedwhen the blend contains the proper proportions of plastic and rubber.Dynamic vulcanization processes are described in U.S. Pat. Nos.3,037,954, 3,806,558, 4,104,210, 4,116,914, 4,130,535, 4,141,863,4,141,878, 4,173,556, 4,207,404, 4,271,049, 4,287,324, 4,288,570,4,299,931, 4,311,628 and 4,338,413.

Known dynamic vulcanization processes are believed to be somewhatunsuitable for making soft compositions because as the rubber levelrises the resulting compositions become less fabricable. In other words,the compositions give poor extrudates and, sometimes, cannot be extrudedat all. Accordingly, there is a need for processes for preparing soft,extrusion-fabricable, thermoplastic elastomeric compositions.

U.S. Pat. No. 4,130,535 discloses thermoplastic vulcanizates or blendsof polyolefin resin and monoolefin copolymer rubber which areprocessable in the same manner as thermoplastics even though the rubberis fully cured. The thermoset state is avoided by simultaneouslymasticating and curing the blends. The blends comprise about 25-95percent by weight of the resin and about 75-5 percent by weight of therubber. Oil extended vulcanizates have a ratio of 35 to 65 percent ofthe resin and about 65 to 35 percent of the rubber. Peroxide, azide andsulfur vulcanizing agents may be used to effect curing of the rubber.Typical monoolefin copolymer rubbers include saturated EPM(ethylene-propylene rubbers) or unsaturated EPDM(ethylene-propylene-diene terpolymer rubbers).

U.S. Pat. No. 4,594,390 teaches that improved thermoplastic elastomermaterials are obtained when a composition comprising polypropylene, anEPDM rubber, an extender oil and a curative is masticated at a shearrate of at least 2000 sec⁻¹. Suitable results are obtained with shearrates of 2500 to 7500 sec⁻¹.

U.S. Pat. No. 4,207,404 discloses thermoplastic elastomer compositionsprepared by dynamic vulcanization of blends of chlorinated polyethyleneand nylon in the presence of a peroxide vulcanizing agent.

U.S. Pat. No. 3,806,558 discloses partially cured blends of a monoolefincopolymer rubber, such as those disclosed in U.S. Pat. No. 4,130,535,and a polyolefin plastic, usually polyethylene or polypropylene. Theblend is mixed with a small amount of curative, and subjected to curingconditions while working the mixture dynamically.

A. Y. Coran, R. P. Patel and D. Williams, in an article entitled"Rubber-Thermoplastic compositions. Part V. Selecting Polymers forThermoplastic Vulcanizates," Rubber Chemistry and Technology, Vol. 55,116 (1982), describe approximately one hundred thermoplastic vulcanizatecompositions, based on nine kinds of thermoplastic resin and elevenkinds of rubber. All compositions contain sixty parts of rubber andforty parts of plastic. They prepare these compositions by melt mixingthe plastic, rubber and other components in a Brabender or Haake mixer.Generally, the plastic, rubber and other components of the composition,except for curatives, are mixed at controlled elevated temperatures(Table I) for about 2-6 minutes during which time the plastic melts anda blend is formed with the rubber. After blend formation, curatives areadded to crosslink the rubber, and mixing is continued until a maximumconsistency or mixing torque is observed. Each composition is removedfrom the mixer and then remixed for an additional minute in the moltenstate to insure uniformity of the mixture. One of the rubber materialsis chlorinated polyethylene (CPE). The plastic materials, listed inTable I on page 117, include polypropylene (PP), polyethylene (PE),polystyrene (PS), an acrylonitrile-butadiene-styrene polymer (ABS), astyrene-acrylonitrile copolymer (SAN), polymethyl methacrylate (PMMA),poly-tetramethylene terephthalate (PTMT), Nylon-6,9 (PA) andpolycarbonate (PC). One of the mechanical properties, tension set (ASTMD412-66), is determined by stretching 51 mm long specimens to 102 mm for10 minutes then by measuring set after 10 minutes relaxation.Chlorinated polyethylene compositions are cured by peroxides,specifically 2,5-dimethyl-2,5-bis(t-butyl peroxy)hexane. Tension setvalues abstracted from Table IX at page 125 are as follows: (a)CPE/PP--55%; (b) CPE/PE--58%; (c) CPE/ABS--65%; (d) CPE/ABS--91%; (e)CPE/PMMA--82%; (f) CPE/PTMT--40%; (g) CPE/PA--59%; and (h) CPE/PC--85%.They note that the 40% value may not be accurate because the CPE isinsufficiently stable to withstand processing at the high melttemperatures for PTMT.

SUMMARY OF THE INVENTION

One aspect of the present invention is a process for preparing athermoplastic elastomer material from a blend of an amorphouschlorinated polyethylene and a crystalline thermoplastic polymer, theprocess comprising:

a. forming a heat-plastified, substantially uniform admixture comprisingan amorphous chlorinated polyethylene, a plasticizing materialcompatible with the chlorinated polyethylene, a crystallinethermoplastic polymer, and a basic material; and

b. dispersing a vulcanizing material for the chlorinated polyethylenethroughout the admixture while mixing said admixture at a temperaturesufficient to activate the vulcanizing package without substantiallydegrading any component of the composition and for a period of timesufficient to cure substantially all of the chlorinated polyethylene,the vulcanizing material comprising (1) a derivative of2,5-dimercapto-1,3,4-thiadiazole or (2) 2,5-dimercapto-1,3,4-thiadiazoleand an activator material.

A related aspect of the present invention is a process for preparing athermoplastic elastomer material from a blend of an amorphouschlorinated polyethylene and a crystalline thermoplastic polymer, theprocess comprising:

a. forming a heat-plastified, substantially uniform admixture comprisingan amorphous chlorinated polyethylene, a plasticizing materialcompatible with the chlorinated polyethylene, a crystallinethermoplastic polymer and a basic material;

b. dispersing a vulcanizing material for the chlorinated polyethylenethroughout the admixture while mixing said admixture at a temperaturesufficient to activate the vulcanizing package without substantiallydegrading any component of the composition and for a period of timesufficient to partially cure the chlorinated polyethylene, thevulcanizing package comprising (1) a derivative of2,5-dimercapto-1,3,4-thiadiazole or (2) 2,5-dimercapto-1,3,4-thiadiazoleand an activator material; and

c. completing vulcanization of the chlorinated polyethylene via staticcuring.

The present invention also relates to the thermoplastic elastomermaterials so prepared. These materials suitably have a tension setvalue, at 100% elongation (ASTM D412), of less than about 50%. Materialshaving tension set values of greater than 50% are believed to beunsuitable for use as elastomers. Thus, a third aspect of the presentinvention is a thermoplastic elastomeric composition comprising a blendof one hundred parts by weight of an amorphous chlorinated polyethyleneresin, from about twelve to about one hundred fifty parts by weight of acrystalline thermoplastic polyolefin resin, and plasticizing material inan amount of from about five to about one hundred fifty parts by weight,the composition being processable in an internal mixer to provide aproduct which forms an essentially continuous sheet following transfer,with the resin components in a heat-plastified state, to the rotatingrolls of a rubber mill.

DESCRIPTION OF PREFERRED EMBODIMENTS

The crystalline thermoplastic polymer is a solid, high molecular weight,resinous plastic material made by polymerizing olefins such as ethylene,propylene, butene-1, pentene-1, 4-methylpentene, and the like byconventional processes. Illustrative polymers include low densitypolyethylene (0.910 to 0.925 grams per cubic centimeter (g/cc)), mediumdensity polyethylene (0.926 to 0.940 g/cc) or high density polyethylene(0.941 to 0.965 g/cc), whether prepared by high pressure processes orlow pressure processes. Polyesters such as polyethylene terephthalatemay also provide suitable results. Particularly suitable polymersinclude the crystalline forms of polypropylene. Crystalline blockcopolymers of ethylene and propylene (which are plastics distinguishedfrom amorphous, random ethylene-propylene elastomers) can also be used.Included among the polyolefin resins are the higher alpha-olefinmodified polyethylenes and polypropylenes (see, "Polyolefins," N. V.Boenig, Elsevier Publishing Co., N.Y. 1966).

Materials other than crystalline thermoplastic polymers may be used inconjunction with the amorphous chlorinated polyethylene provided suchmaterials are mechanically compatible with the chlorinated polyethylene."Mechanically compatible", as used herein, means that the polymers forma two phase mixture that does not undergo substantial delamination.Illustrative materials believed to meet this criterion include glassypolymers such as polycarbonates, styrene-acrylonitrile copolymers andterpolymers of acrylonitrile, butadiene and styrene.

Chlorinated polyethylene starting materials suitable for purposes of thepresent invention are finely-divided particles which must meet fourphysical property criteria. First, the materials must have a weightaverage molecular weight of from about 40,000 to about 300,000. Second,the materials must have a chemically combined chlorine content of fromabout 20 to about 48 percent by weight of polymer. Third, the materialsmust have a 100 percent modulus, measured in accordance with ASTM TestD-412, from about 0.5 to about 4.8 MPa. Fourth, the materials must havea relative crystallinity of from about 0 to about 15 percent, preferablyfrom about 0 to about two percent.

Chlorinated polyethylene materials meeting the aforementioned physicalproperty criteria can be prepared by a chlorinated procedure of the typedisclosed in U.S. Pat. No. 3,454,544, the teachings of which areincorporated herein by reference thereto.

Satisfactory chlorinated polyethylene resins are readily obtained bypractice of a chlorination procedure which comprehends suspensionchlorination, in an inert medium, of a finely divided, essentiallylinear polyethylene or olefin interpolymer. The interpolymer contains atleast about 90 mole percent ethylene with the remainder being one ormore ethylenically unsaturated monomers polymerizable therewith. Thepolymer is first chlorinated at a temperature below its agglomerationtemperature for a period of time sufficient to provide a partiallychlorinated polymer having a chlorine content of from about 2 to 23percent chlorine, based on the total weight of polymer. This is followedby sequential suspension chlorination of the partially chlorinatedpolymer, in a particulate form, at a particular temperature. Theparticular temperature is, with respect to the olefin interpolymer,above its agglomeration, temperature but at least about 2° Centigradebelow its crystalline melting point. Sequential chlorination iscontinued for a period of time sufficient to provide a chemicallycombined chlorine content of up to about 48 percent by weight ofpolymer.

Useful ethylenically unsaturated monomers include non-aromatichydrocarbon olefins having three or more carbon atoms such as propylene,butene-1, 1,4-hexadiene, 1,5-hexadiene, octene-1, 1,7-octadiene,1,9-decadiene and the like; substituted olefins such as acrylic acid,acrylic acid esters and the like; alkenyl aromatic compounds such asstyrene and its derivatives, and other known polymerizable materials.

The temperature at which chlorination normally leads to agglomeration ofpolymer particles depends to a large extent on the nature and molecularweight of the polymer to be chlorinated. In the case of crystalline andpredominantly straight chain polyethylenes having a branching of thechains of less than one methyl group per 100 carbon atoms and a densityof at least 0.94 grams per cubic centimeter, the temperature is above95° Centigrade, in particular above 100° Centigrade or even about about110° Centigrade. In the case of polyethylenes having a relatively markedbranching of the chains and a lower density, the temperature is lower,about 65° Centigrade.

The temperature employed in the sequential chlorination must be greaterthan that employed in the initial chlorination in order to prevent (a)retention of excessive undesirable crystallinity and (b) formation ofnonuniformly chlorinated polymer. The temperature employed in thesequential chlorination must also be below the crystalline melting pointof the polymer being chlorinated in order to prevent acceleratedparticle size growth and development of undesirable agglomeration ofpolymer particles.

After a polyolefinic material has been suspension chlorinated to adesired degree, it may easily be filtered from suspension in the inertsuspending liquid, washed and dried to prepare it for subsequent use.

The present invention is not restricted to chlorinated polyethyleneresins prepared by suspension or slurry chlorination procedures.Solution chlorination and bulk, or fluidized bed, chlorinationprocedures may also be used provided the polymers produced thereby meetthe aforementioned requirements with regard to chlorine content andresidual crystallinity.

The thermoplastic elastomers or vulcanizates of the present inventionare suitably cured with a cure package comprising a basic material and2,5-dimercapto-1,3,4-thiadiazole or a derivative thereof. These curepackages are disclosed in U.S. Pat. Nos. 4,128,510 and 4,288,576, theteachings of which are incorporated herein by reference thereto.

Peroxide cure packages are believed to be unsuitable for use in curingblends as disclosed herein, particularly where the crystalline olefinpolymer is polypropylene. Physical properties and handlingcharacteristics of the blends indicate either a lack of sufficientcrosslinking or at least partial degradation of the polypropylene.

Illustrative derivatives of 2,5-dimercapto-1,3,4-thiadiazole include:##STR1## wherein X is a substituent selected from hydrogen, --CRR'OH,--(CH₂ --CH--O)_(n) H, ##STR2## where m is an integer of from 2 to 10; nis an integer from 1 to 5; R and R' are selected from hydrogen, alkylgroups containing 1-8 carbon atoms, and aryl, alkaryl or aralkyl groupscontaining 6 to 8 carbon atoms; R² is an alkyl group containing 1-17carbon atoms, an aryl group containing one or two rings, an alkarylgroup containing 7-14 carbon atoms, an aralkyl group containing 7-8carbon atoms or a cyclohexyl group; and R³ is an alkyl group containing1-8 carbon atoms. X' can be the same as X with the exception of hydrogenand Y is zinc, lead, ##STR3## where R⁴ is an alkylene or alkenylenegroup containing 1-8 carbon atoms, or a cycloalkylene, arylene or aalkarylene group containing 6-8 carbon atoms; z is 0 or 1; and R⁵ is analkylene group containing 2-8 carbon atoms or a phenylene,methylphenylene or methylenediphenylene group.

Basic materials suitable for use in conjunction with derivatives of2,5-dimercapto-1,3,4-thiadiazole include inorganic materials such asbasic metal oxides and hydroxides and their salts with weak acids, suchas, for example, magnesium hydroxide, magnesium oxide, calcium oxide,calcium hydroxide, barium oxide, barium carbonate, sodium phenoxide andsodium acetate. These basic materials also serve as heat stabilizers forchlorinated polyethylene. Thus, they are beneficially admixed with thechlorinated polyethylene before the polymer blend is converted to aheat-plastified admixture rather than in conjunction with thethiadiazole derivative. Additional basic material may, if desired, beadded together with the thiadiazole derivative. Other basic materialsmay also be used so long as they do not promote degradation of one ofthe components of the blend or deactivate the vulcanizing materials. Thebasic material is preferably magnesium oxide or magnesium hydroxide.

Basic or activator materials suitable for use in conjunction with2,5-dimercapto-1,3,4-thiadiazole include (1) amines having a boilingpoint above about 110° C., and a pK value below about 4.5; (2) salts ofamines having pK values below about 4.5 with acids having pK valuesabove about 2.0; (3) quaternary ammonium hydroxides and their salts withacids having pK values above about 2.0; (4) diphenyl- andditolylguanidines; and (5) the condensation product of aniline and atleast one mono-aldehyde containing one to seven carbon atoms, incombination with at least an equal amount of an inorganic base. The term"pK value" refers to the dissociation constants of bases and acids inaqueous solution. Representative values are shown in the Handbook ofChemistry and Physics, 45th Edition, The Chemical Rubber Co., page D-76(1964). As noted in the preceding paragraph, a certain amount of a basicmaterial such as magnesium oxide or magnesium hydroxide must also bepresent to heat stabilize the chlorinated polyethylene.

The plasticizing material is suitably selected from the group consistingof trimellitate esters, phthalate esters, aromatic oils and polyestersof dicarboxylic acids containing from about two to about ten carbonatoms. The plasticizing material is desirably trioctyl trimellitate.

The ingredients save for the vulcanizing material are mixed at atemperature sufficient to soften the crystalline thermoplastic polymeror, more commonly, at a temperature above its melting point if thepolymer is crystalline at ordinary temperatures. Blending is carried outfor a time sufficient to form a generally uniform blend of thecomponents. It is accomplished by any one of a number of conventionaltechniques, for example, in an internal mixer, two-roll mill orextruder. After the resin and rubber are intimately mixed, thevulcanizing material is added. Heating and masticating the blendcomponents at vulcanization temperatures are generally adequate tocomplete curing in a few minutes. If shorter vulcanization times aredesired, higher temperatures may be used, provided they are low enoughto preclude substantial degradation of the chlorinated polyethylene.

Suitable vulcanization temperatures range from about the meltingtemperature of the crystalline thermoplastic polymer (about 130° C. inthe case of polyethylene and about 175° C. in the case of polypropylene)to 250° C. or more. Typically, the range is from about 150° C. to 225°C. A preferred range of vulcanization temperatures is from about 180° toabout 200° C. Thermoplastic vulcanizates are beneficially prepared bycontinuously mixing the compositions, after the vulcanizing material isadded, until vulcanization is complete.

If desired from an economic point of view, completion of vulcanizationmay be accomplished by static vulcanization provided sufficient curingby dynamic vulcanization has occurred before static vulcanizationbegins. If insufficient dynamic vulcanization occurs, an unprocessablethermoset vulcanizate may be obtained.

Physical property values from a hybrid of dynamic vulcanization andstatic vulcanization, where adequate dynamic vulcanization has occurred,do not differ appreciably from those obtained from blends cured solelyby dynamic vulcanization. By way of illustration, sufficient dynamicvulcanization occurs in as little as one minute in a heated mixeroperating at a temperature of about 400° F. (about 204° C.) if thecomponents of the blend are premixed. Without premixing, five minutes oreven longer may be required to achieve sufficient dynamic vulcanizationin such a heated mixer. If appreciable static curing occurs before therubber is dispersed and the thermoplastic becomes a continuous phase, anunprocessable thermoset vulcanizate may be obtained.

A convenient measure of the state of cure of the thermoplastic elastomercompositions of the present invention is obtained by comparing thetensile strength of the blend before and after dynamic vulcanization.The dynamically vulcanized blend using a thiadiazole cure packagesuitably has a tensile strength of about 1.3 megapascals (MPa) anddesirably 3.4 MPa or more greater than that of the unvulcanized blend orthe peroxide cured blend.

The properties of the thermoplastic vulcanizates of this invention maybe modified, either before or after vulcanization, by adding ingredientswhich are conventional in the compounding of chlorinated polyethyleneelastomers, polyolefin resins and blends thereof. Skilled artisans willrecognize, however, that chlorinated polyethylene compounding additivesgenerally must be added before vulcanization if they are to have aneffect upon the chlorinated polyethylene. The timing of addition is notas critical for addition of ingredients to the thermoplastic portion ofthe materials of the present invention.

Examples of suitable ingredients or additives include various carbonblacks, alumina, silica, titanium dioxide, calcium carbonate, coloredpigments, clays, zinc oxide, stearic acid, accelerators, vulcanizingagents, sulfur, stabilizers, antioxidants, antidegradants, processingaids, adhesives, tackifiers, plasticizers, processing aids such aslubricants and waxes, prevulcanization inhibitors, discontinuous fiberssuch as glass fibers and wood cellulose fibers, and extender oils. Theamounts used depend, at least in part, upon the quantities of otheringredients in the composition and the properties desired from thecomposition. Minor amounts of other saturated and unsaturated polymerssuch as alpha-olefins may be added to reduce the cost or modify theproperties of the composition.

The addition of carbon black, or an extender oil or both is recommended,particularly if accomplished prior to dynamic vulcanization. Carbonblack improves the tensile strength and extender oil can improve theresistance to oil swell, heat stability, hysteresis, cost and permanentset of the thermoplastic vulcanizate. The addition of extender oil canalso improve processability.

Aromatic, naphthenic and paraffinic extender oils provide satisfactoryresults so long as they are used in amounts which do not exceed theirlimits of compatibility with chdlorinated polyethylene. Suitableextender oils are identified in Rubber World Blue Book, Materials andCompounding Ingredients for Rubber (1975), pages 145-190. The quantityof extender oil added depends upon the properties desired. The upperlimit, which depends upon the compatibility of a particular oil andblend ingredients, is exceeded when excessive exudation of extender oiloccurs. Typically, 5-150 parts by weight extender oil are added per 100parts by weight of chlorinated polyethylene. Commonly, from about 30 toabout 125 parts by weight of extender oil are added per 100 parts byweight of chlorinated polyethylene present in the blend with quantitiesof from about 70 to 100 parts by weight of extender oil per 100 parts byweight of chlorinated polyethylene being preferred.

Typical additions of carbon black comprise about 40-250 parts by weightof carbon black per 100 parts by weight of chlorinated polyethylene andusually about 20-100 parts by weight carbon black per 100 parts byweight of chlorinated polyethylene. The amount of carbon black which canbe used depends, at least in part, upon the type of carbon black andupon the amount of extender oil to be used.

Thermoplastic elastomeric vulcanizates prepared as described herein areuseful for making a variety of articles such as tires, hoses, belts,gaskets, moldings and molded parts. They are particularly useful formaking articles by extrusion, injection molding and compression moldingtechniques. They also are useful for modifying thermoplastic resins ingeneral and polyolefin resins in particular. The vulcanizates aresuitably blended with thermoplastic resins using conventional mixingequipment. The properties of the modified resin depend upon the amountof vulcanizate blended. Generally, the amount of vulcanizate issufficient to provide from about 5 to 25 parts by weight of chlorinatedpolyethylene per hundred parts by weight of the modified resin.

The following examples are for purposes of illustration only and are notto be construed as limiting the scope of the present invention. Allparts and percentages are by weight unless otherwise specified. Arabicnumerals are used to identify examples representing the presentinvention whereas alphabetic characters are used to designatecomparative examples.

SAMPLE PREPARATION

A 1450 cubic centimeter (cc) capacity Banbury mixer is used to provideinitial melt compounding of all blends and, when appropriate curativecomponents are added and activated, at least partial curing of saidblends. Further mixing and, if needed, completion of curing takes placewhen the contents of the Banbury mixer are placed on a heated two rollmill. Curing may also be completed in a static cure oven.

A. Multiple Step Banbury Mix Procedure

1. Prepare a rubber masterbatch by adding chlorinated polyethylene,stabilizers, fillers, plasticizers and other additives to the Banburymixer while it is operating at low speed (about 77 revolutions perminute (rpm)) and cooling water is circulating through the front andrear rotors, right and left sides and fixed sections of the Banburymixer. As noted hereinabove, the base to be used in conjunction with thevulcanizing material may also function as the stabilizer. The amounts ofmasterbatch components are sufficient to fill the mixing cavity. Mixingcontinues for about four minutes at which time the temperature of thecontents reaches 325° Fahrenheit (°F.) (approximately 163° C.).

2. Remove part of the masterbatch, replace it with an amount ofcrystalline thermoplastic polymer and continue mixing for about fiveminutes at a temperature of about 350° F. (approximately 176° C.). Thetemperature of the contents is controlled by varying the mixer speed.

3. Remove the blend from the Banbury mixer and place it on a two rollrubber compounding mill operating at a set temperature of about 70° F.(approximately 21° C.) with a gap between the rolls of about 200 mils (5millimeters (mm)).

4. After cooling the blend on the two roll mill for a period of abouttwo minutes, add components to be used in vulcanizing the blend (alsoknown as the "cure package") and continue mixing for a period of abouttwo minutes.

5. Remove the roll milled blend (also known as "the blanket") from thetwo roll mill, cut it into strips and add the strips to the Banburymixer which is operating at a set temperature of from about 350° F.(approximately 176° C.) to about 370° F. (approximately 188° C.). Mixingand curing of the CPE continues for about seven minutes with temperaturecontrol as in step 2. This period of time is generally sufficient tocompletely cure the CPE component of the blend.

6. Remove the contents of the Banbury mixer and mix for two minutes on ahot two roll mix (heated with 150 pounds per square inch (psi) steam)with a gap between the rolls of about 200 mils (5 millimeters (mm)).This final mixing on the roll mill is done to assure that uniformsamples are used to prepare compression molded samples for testing.Remove the contents from the mill in the form of a sheet having athickness of about 65 mils (approximately 1.7 mm).

7. Compression mold the sheets to a thickness of 60 mils (approximately1.5 mm) using a heated (372° F. (approximately 189° C.)) press. Thepress and its contents are first preheated with no applied force for twominutes. The contents are then pressed for three minutes with an appliedforce of twenty tons, cooled for four minutes with an applied force oftwenty tons and then removed from the press after the force is relieved.The compression molded sheets are used for physical propertycharacterization.

B. Single Load Banbury Mix Procedure

1. Same as step 1 of the Multiple Step Banbury Mix Procedure except thatthe mixer is not completely filled with rubber masterbatch components.In other words, there is sufficient room to add the crystallinethermoplastic polymer without the necessity of removing a portion of themasterbatch.

2. Add an amount of crystalline thermoplastic polymer and continuemixing for about five minutes at a temperature of about 350° F.(approximately 176° C.). The amount is generally sufficient to fill themixer. The temperature of the contents is controlled by varying themixer speed.

3. Add the vulcanizing material to the blend while continuing mixing.The vulcanizing material is placed in a small bag formed from anethylene/acrylic acid copolymer commercially available from The DowChemical Company under the trade designation Primacor™. The bag is usedto minimize, if not eliminate, loss of vulcanizing material to the wallof the mixer. Mixing and curing continues for about seven minutes at atemperature of from about 350° F. to about 370° F. (from about 176° C.to about 188° C.). As noted herein, at step 5 of the Multiple StepProcedure, this period of time is generally sufficient to completelycure the CPE component of the blend.

4. Same as step 6 of the Multiple Step Banbury Mix Procedure.

5. Same as step 7 of the Multiple Step Banbury Mix Procedure.

Test Procedures

The following American Society for Testing and Materials (ASTM) Testsare used to characterize the physical properties of materials preparedin accordance with procedures A and B above:

Specific Gravity: ASTM Method D792

Hardness: ASTM Method D2240

Tensile Strength: ASTM Method D412

Elongation: ASTM Method D412

Modulus: ASTM Method D412

Tension Set: ASTM Method D412

Compression Set: ASTM Method D395B

Oil Resistance: ASTM Method D471

Heat Resistance: ASTM Method D573

EXAMPLES 1-3 CPE/PP Thermoplastic Elastomer

Using the Multiple Step Banbury Mix Procedure (Procedure A) or theSingle Load Banbury Mix Procedure (Procedure B), sample sheets areprepared from the composition shown in Table I. In Example 1, the amountof trioctyl trimellitate is 85 parts and the amount of polypropylene is56.0 parts. In Examples 2 and 3, the amount of trioctyl trimellitate is100 parts and the amount of polypropylene is 59.9 parts.

Physical property test values obtained from said sample sheets aresummarized in Table II.

                  TABLE I                                                         ______________________________________                                        EXAMPLE 1 COMPOSITION                                                         Parts/Hundred                                                                 Parts of CPE                                                                            Component Description/Source-Purpose                                ______________________________________                                        30        carbon black N330 - filler material                                 5.2       hydrated amorphous silica, commercially                                       available from PPG Industries, Inc. under                                     the trade designation HiSil ™ 223 - filler                                 material                                                            5.2       magnesium oxide, commercially available                                       from Elastochem Inc. under the trade                                          designation Maglite ™ D - activator                              85 or 100 trioctyltrimellitate - oil extender                                 100       chlorinated polyethylene, commercially                                        available from The Dow Chemical Company                                       under the trade Designation Tyrin ™ CM0136 -                               rubber                                                              56.0 or 59.9                                                                            polypropylene, commercially available                                         from Himont, Inc. under the trade desig-                                      nation Pro-fax ™ 6723 - thermoplastic                            3.0       5-mercapto-1,3,4-thiadiazole-2-                                               thiobenzoate, commercially available from                                     Hercules Inc. under the trade designation                                     Echo-S ™ curative                                                0.9       condensation product of analine and                                           butyraldehyde commercially available from                                     R. T. Vanderbilt Co., Inc. under the                                          trade designation Vanax ™ 808 - curative                                   accelerator                                                         ______________________________________                                    

                  TABLE II                                                        ______________________________________                                        Physical Property Data for Examples 1-3                                       Process/Physical Property                                                                      Physical Property Measured Value                             (Unit of Measure)                                                                              Ex. 1    Ex. 2    Ex. 3                                      ______________________________________                                        Process          A        A        B                                          Specific Gravity 1.12     1.11     1.11                                       Hardness, Shore A                                                                              80       78       82                                         Ultimate Tensile 1128/7.8*                                                                              1087/7.5*                                                                              1192/8.2                                   (psi/MPa)                                                                     Elongation (%)   258*     292*     256                                        100% Modulus (psi/MPa)                                                                         608/4.2* 548/3.8* 670/4.6                                    200% Modulus (psi/MPa)                                                                         946/6.5* 836/5.8* 997/6.9                                    Tension Set @ 100% Elong.                                                                      16       15       15                                         Compression Set  60       63       65                                         212° F./70 Hours                                                       ASTM Oil 2,                                                                   250° F./70 Hours                                                       Volume Swell (%) 8        5        4                                          % Tensile Retained                                                                             66       62       79                                         % Elong. Retained                                                                              80       57       69                                         % 100% Mod. Ret. 86       99       91                                         ASTM Oil 3,                                                                   250° F./70 Hours                                                       Volume Swell (%) 24       20       19                                         % Tensile Retained                                                                             54       57       61                                         % Elong. Retained                                                                              66       64       70                                         % 100% Mod. Ret. 62       74       77                                         ______________________________________                                         *Average of two test samples                                             

The data presented in Table II demonstrate that similar results areobtained by the single step and multi-step processes. The data alsodemonstrate that satisfactory results are obtained with two differentlevels of trioctyl trimellitate. Similar results are expected with othercompositions and process variations which fall within the scope of thepresent invention.

EXAMPLE 4 AND COMPARATIVE EXAMPLES A-B Cure System Comparison

Using the Single Load Banbury Mix Procedure (Procedure B), sample sheetsare prepared from compositions similar to that shown in Table I. InExample 4 and Comparative Examples A and B, the amount of trioctyltrimellitate is 100 parts and the amount of polypropylene is 59.9 parts.In Example 4, the amount of accelerator is increased to 1.0 part. InComparative Example A, no cure package is used and in ComparativeExample B, curing is accomplished with a peroxide cure package. Theperoxide cure package includes 6.0 parts ofα-α'-bis(t-butylperoxy)diisopropylbenzene on Burgess KE Clay,commercially available from Hercules Inc. under the trade designationVul-Cup™ 40KE and 2.0 parts of triallyl trimellitate (commerciallyavailable from C. P. Hall). Physical property test values obtaained fromsaid sample sheets are summarized in Table III.

                  TABLE III                                                       ______________________________________                                        Cure System Comparison                                                        Process/Physical Property                                                                    Physical Property Measured Value                               (Unit of Measure)                                                                            Ex. 4   Comp Ex. A Comp Ex. B                                  ______________________________________                                        Process        B       B          B                                           Specific Gravity                                                                             1.11    1.10       1.12                                        Hardness, Shore A                                                                            80      78         75                                          Ultimate Tensile                                                                             1137/   937/       471/                                        (psi/MPa)      7.8     6.5        3.2                                         Elongation (%) 257     533        197                                         100% Modulus (psi/MPa)                                                                       665/4.6 518/3.6    372/2.6                                     200% Modulus (psi/MPa)                                                                       963/6.6 601/4.1    --                                          Tension Set @ 100%                                                                           16      28         22                                          Elong.                                                                        Compression Set                                                                              56      87         90                                          212° F./70 Hours                                                       ASTM Oil 2,                                                                   250° F./70 Hours                                                       Volume Swell (%)                                                                             5       13         21                                          % Tensile Retained                                                                           69      51         51                                          % Elong. Retained                                                                            65      24         21                                          % 100% Mod. Ret.                                                                             96      84         --                                          ASTM Oil 3,                                                                   250° F./70 Hours                                                       Volume Swell (%)                                                                             20      47         42                                          % Tensile Retained                                                                           60      34         18                                          % Elong. Retained                                                                            60      18         17                                          % 100% Mod. Ret.                                                                             81      --         --                                          ______________________________________                                         -- not measured                                                          

The data presented in Table III demonstrate that physical properties areimproved when the CPE/PP blends are cured with a thiadiazole cure. Thedata also demonstrate that physical properties are degraded when theblends are cured with a conventional peroxide cure package. Similarresults are obtained with other compositions within the scope of thepresent invention.

COMPARISON EXAMPLES C-F Commercial Thermoplastic Elastomer PhysicalProperties

In order to evaluate the potential suitability of the thermoplasticelastomers of the present invention, four commercially availablethermoplastic elastomers are subjected to the same tests as Examples 1and 2. Comparative Example C is Santoprene™ 201(73), commerciallyavailable from Monsanto Co. Comparative Example D is Santoprene™201(80), commercially available from Monsanto Co. Comparative Example Eis Alcryn™ 1201B, an oil resistant thermoplastic elastomer commercialavailable from E. I. DuPont de Nemours & Co. Comparative Example F isGeolast™ 701, an oil resistant thermoplastic elastomer commerciallyavailable from Monsanto Co. The test results are presented in Table IVwhich follows. Example 1 is included in Table IV for ease of comparison.

                  TABLE IV                                                        ______________________________________                                        Physical Property Comparison                                                  Process/Physical                                                                           Physical Property Measured Value                                 Property (Unit       Comp    Comp  Comp  Comp                                 of Measure)  Ex 1    Ex C    Ex D  Ex E  Ex F                                 ______________________________________                                        Specific Gravity                                                                           1.12    .968    .966  1.23  1.09                                 Hardness,    80      76      80    65    80                                   Shore A                                                                       Ult. Tens.   1123/   1451/   1494/ 1796/ 1339/                                psi/MPa      7.8*    10.0    10.3  12.4  9.2                                  Elongation % 258*    513     415   280   200                                                                     309   294                                  100% Mod,    608/    472/    598/  608/  548/                                 psi.MPa      4.2*    3.3     4.1   4.2*  3.8*                                 200% Mod,    946/    607/    813/  1162/ 1246/                                psi.MPa      6.5*    4.2     5.6   8.0*  8.6*                                 Tension Set                                                                   at 100% Elong.                                                                             16      15      10    6     12                                   Compression Set                                                                            60      40      40    59    50                                   212° F./70 hours                                                       Low Temp Britt ° C.                                                                 -36     -60**   -60** -35   -38                                  ASTM Oil 2, 250°                                                       F./70 Hr                                                                      Vol Swell %  8       46      40    4     2                                    % Tens Ret   66      68      77    103   97                                   % Elong Ret  80      64      76    93    79                                   % 100% Mod Ret                                                                             86      86      101   94    109                                  ASTM Oil 3, 250°                                                       F./70 Hr                                                                      Vol Swell %  24      65      59    17    13                                   % Tens Ret   54      61      74    82    71                                   % Elong Ret  66      58      74    78    61                                   % 100% Mod Ret                                                                             62      75      95    85    90                                   ______________________________________                                         *average of two test samples                                                  **reported by manufacturer                                               

The data presented in Table IV demonstrate that the thermoplasticelastomers of the present invention compare favorably with commerciallyavailable materials in terms of physical properties such as tension setat 100% elongation, tensile, elongation, oil resistance and lowtemperature impact resistance.

EXAMPLES 5-9 Effect of Different Polypropylene on Properties

Using the Single Mix Procedure (Procedure B), sample sheets wereprepared from a composition similar to that shown in Table I. The typeand amount of filler materials, chlorinated polyethylene, curative andcurative co-agent are the same. The amount of trioctyltrimellitate isone hundred parts. The following polypropylenes are used in amount of59.9 parts: PP-A is Pro-fax™ 6723, 0.8 g/10 min. melt index; PP-B isPro-fax™ 6524, 4.0 g/10 min. melt index; PP-C is Pro-fax™ 6324, 12.0g/10 min. melt index; PP-D is Pro-fax™ 6301, 12.0 g/10 min. meltindex--unstabilized; and PP-E is Pro-fax™ 6624, 35.0 g/10 min. meltindex.

Physical property test values together with the type of polypropyleneare shown in Table V.

                                      TABLE V                                     __________________________________________________________________________    Effect of Different Types of Polypropylene on Properties                      Process/Physical Property                                                                   Physical Property Measured Value                                (Unit of Measure)                                                                           Ex. 5                                                                              Ex. 6                                                                              Ex. 7                                                                             Ex. 8                                                                              Ex. 9                                        __________________________________________________________________________    PP Type       A    B    C   D    E                                            Specific Gravity                                                                            1.11 1.11 1.11                                                                              1.11 1.11                                         Hardness, Shore A                                                                           86   86   85  86   86                                           Ultimate Tensile (psi/MPa)                                                                  1105/7.6                                                                           1107/7.6                                                                           978/6.7                                                                           926/6.4                                                                            657/4.5                                      Elongation (%)                                                                              290  225  232 229  189                                          100% Modulus (psi/MPa)                                                                      710/4.9                                                                            853/5.9                                                                            689/4.8                                                                           687/4.7                                                                            657/4.5                                      200% Modulus (psi/MPa)                                                                      989/6.8                                                                            1057/7.3                                                                           879/6.1                                                                           886/6.1                                                                            --                                           Tension Set @ 100% Elong.                                                                   25   24   27  26   23                                           Compression Set                                                                             73   70   85  80   75                                           212° F./70 Hrs                                                         ASTM Oil 2, 250° F./70 Hrs                                             Volume Swell (%)                                                                            4    4    5   4    3                                            % Tensile Retained                                                                          62   49   42  50   46                                           % Elong. Retained                                                                           45   36   35  37   34                                           ASTM Oil 3, 250° F./70 Hrs                                             Volume Swell (%)                                                                            21   21   24  23   19                                           % Tensile Retained                                                                          52   44   36  39   39                                           % Elong. Retained                                                                           44   36   29  22   24                                           __________________________________________________________________________     -- cannot be measured                                                    

The data presented in Table V demonstrate that high molecular weightpolypropylenes (e.g. Ex. 5) produce thermoplastic elastomer materialswith higher tensile strength and elongation than lower molecular weightpolypropylenes (Ex. 9). The higher molecular weight polypropylenes alsohave greater tensile strength and elongation values after exposure tooils even though percent property retention does not vary significantly.Similar results are obtained when samples are exposed to air oven agingas well as with other polymer blend compositions within the scope of thepresent invention.

EXAMPLES 10-15 Effect of Extender Oil Type Upon Physical Properties

Using the Single Load Banbury Mix Procedure (Procedure B) and, with twoexceptions, the composition of Example 4, sample sheets are prepared forphysical property testing. One exception is that, for Examples 10-15,the magnesium oxide is changed to a magnesium hydroxide commerciallyavailable under the trade designation Marinco™ H from Calgon. The secondexception is in the type of extender oil. The extender oils are asfollows: Example 10--TOTM; Example 11--a high boiling aromatic oilcommercially available from R. E. Carroll under the trade designationPolyflo™ 1172 (hereinafter "AR-1"); Example 12--a high boiling aromaticoil commercially available from R. E. Carroll under the tradedesignation Sundex™ 8600T (hereinafter "AR-2"); Example 13--a highboiling aromatic oil commercially available under the trade designationSundex™ 8125 (hereinafter "AR-3); Example 14--an aromatic oilcommercially available from R. E. Carroll under the trade designationSundex™ 790 (hereinafter "AR-4"); and Example 15--dioctyl phthalate(hereinafter "DOP"). Physical property test results are summarized inTable VI.

                                      TABLE VI                                    __________________________________________________________________________    Effect of Extender Oil Type                                                   Process/Physical Property                                                                   Physical Property Measured Value                                (Unit of Measure)                                                                           Ex. 10                                                                             Ex. 11                                                                             Ex. 12                                                                            Ex. 13                                                                             Ex. 14                                                                            Ex. 15                                   __________________________________________________________________________    Type Oil      TOTM AR-1 AR-2                                                                              AR-3 AR-4                                                                              DOP                                      Specific Gravity                                                                            1.11 1.15 1.10                                                                              1.12 1.10                                                                              1.11                                     Hardness, Shor A                                                                            86   85   85  87   79  82                                       Ultimate Tensile (psi/MPa)                                                                  1105/7.6                                                                           1292/8.9                                                                           923/6.4                                                                           1053/7.3                                                                           891/6.1                                                                           1016/7.0                                 Elongation (%)                                                                              290  314  216 271  239 245                                      100% Modulus (psi/MPa)                                                                      710/4.9                                                                            712/4.9                                                                            709/4.9                                                                           719/5.0                                                                            556/3.8                                                                           649/4.5                                  200% Modulus (psi/MPa)                                                                      989/6.8                                                                            1035/7.1                                                                           899/6.2                                                                           940/6.5                                                                            789/5.4                                                                           909/6.3                                  Tension Set @ 100% Elong.                                                                   25   30   28  28   16  16                                       Compression Set                                                                             73   77   80  82   72  68                                       212° F./70 Hrs                                                         ASTM Oil 2, 250° F./70 Hrs                                             Volume Swell (%)                                                                            2    2    9   5    2   4                                        % Tensile Retained                                                                          62   55   51  54   72  59                                       % Elong. Retained                                                                           45   41   42  39   53  44                                       % 100% Mod. Ret.                                                                            75   84   --  74   --  88                                       ASTM Oil 3, 250° F./70 Hrs                                             Volume Swell (%)                                                                            20   22   27  23   19  21                                       % Tensile Retained                                                                          52   43   48  45   58  50                                       % Elong. Retained                                                                           44   34   50  38   58  50                                       % 100% Mod. Ret.                                                                            67   73   57  64   77  69                                       __________________________________________________________________________     -- not measured                                                          

The data presented in Table VI show that physical property values aregenerally acceptable for all types of extender oils. The aromatic oilsare not as compatible as TOTM with the blends. As such, some bleeding tothe surface is observed when aromatic oils are used. The aromatic oilsalso have less resistance to physical property degradation followingthermal aging than TOTM. In addition, low temperature properties arepoorer when aromatic oils are used rather than TOTM or DOP or otherester plasticizers. DOP suffers from a similar loss of physicalproperties following thermal aging. The loss of physical propertiesfollowing thermal aging, while rendering such compounds unsuitable forhigh temperature applications such as are experienced in an automobileengine compartment, are not important if the compounds are subjectedonly to comparatively low temperatures. Similar results are expectedwith other compounds which are representative of the present invention.

EXAMPLES 16-34 Cure Program Variability

Using the composition of Example 4 except that the amount ofpolypropylene is 60 parts, a variety of cure programs using only dynamiccuring (in the Banbury mixer) or a combination of dynamic curing andstatic curing (in a heated oven) are evaluated. Results of theevaluation are shown in Table VII.

                                      TABLE VII                                   __________________________________________________________________________    Cure Program Variability, Examples 16-21                                                       Example No.                                                                   16    17    18   19    20    21                              __________________________________________________________________________    CURE PROGRAM (MINUTES)                                                        Mix Rubber Component                                                                           3     3     3    3     3     3                               Add PP then Mix  4     4     4    4     4     4                               Dynamic (Mixer) Cure Time                                                                      1     1     1    3     3     3                               Roll Mill Time   1     1     1    1     1     1                               Static (Oven) Cure Time                                                                        0     4     6    0     2     4                               Roll Mill Time   2     2     2    2     2     2                               Total Mixer Time 8     8     8    10    10    10                              Total Cure Time  1     5     7    3     5     7                               PHYSICAL PROPERTIES                                                           Ultimate Tensile (psi/mPa)                                                                     1270/8.8                                                                            1293/8.9                                                                            1300/9.0                                                                           1224/8.4                                                                            1225/8.7                                                                            1312/9.0                        Elongation (%)   326   307   325  310   317   324                             100% Modulus (psi/mPa)                                                                         718/5.0                                                                             737/5.1                                                                             725/5.0                                                                            712/4.9                                                                             703/4.8                                                                             716/4.9                         200% Modulus (psi/mPa)                                                                         1014/7.0                                                                            1061/7.3                                                                            1031/7.1                                                                           980/6.8                                                                             988/6.8                                                                             1002/6.9                        Tension Set @ 100% Elong.                                                                      25    23    25   28    25    25                              Compression Set  69    69    68   73    83    78                              (212° F./70 hrs)                                                       ASTM OIL #2, 250° F./70 Hrs                                            Volume Swell %   5     4     5    6     7     6                               % Tensile Retained                                                                             58    64    51   52    46    57                              % Elongation Retained                                                                          33    44    28   33    27    41                              ASTM OIL #3, 250° F./70 Hrs                                            Volume Swell %   22    22    23   24    25    24                              % Tensile Retained                                                                             49    51    50   43    43    48                              % Elongation Retained                                                                          36    44    40   36    34    44                              __________________________________________________________________________    Cure Program Variability, Examples 22-27                                                       Example No.                                                                   22    23    24   25    26    27                              __________________________________________________________________________    CURE PROGRAM (MINUTES)                                                        Mix Rubber Component                                                                           3     3     3    3     0     0                               Add PP then Mix  4     4     4    4     4     4                               Dynamic (Mixer) Cure Time                                                                      5     5     5    7     1     1                               Roll Mill Time   1     1     1    1     1     1                               Static (Oven) Cure Time                                                                        0     2     4    0     0     2                               Roll Mill Time   2     2     2    2     0     0                               Total Mixer Time 12    12    12   14    5     5                               Total Cure Time  5     7     9    7     1     3                               PHYSICAL PROPERTIES                                                           Ultimate Tensile (psi/mPa)                                                                     1211/8.3                                                                            1274/8.8                                                                            1206/8.3                                                                           1290/8.9                                                                            1197/8.3                                                                            1218/8.4                        Elongation (%)   292   318   296  300   276   290                             100% Modulus (psi/mPa)                                                                         703/4.8                                                                             723/5.0                                                                             692/4.8                                                                            764/5.3                                                                             750/5.2                                                                             722/5.0                         200% Modulus (psi/mPa)                                                                         986/6.8                                                                             999/6.9                                                                             966/6.7                                                                            1033/7.1                                                                            1032/7.1                                                                            1003/6.9                        Tension Set @ 100% Elong.                                                                      28    28    25   23    25    25                              Compression Set  69    74    74   74    83    86                              (212° F./70 hrs)                                                       ASTM OIL #2, 250° F./70 Hrs                                            Volume Swell %   6     6     5    7     6     7                               % Tensile Retained                                                                             52    58    55   59    52    46                              % Elongation Retained                                                                          36    38    41   45    34    28                              ASTM OIL #3, 250° F./70 Hrs                                            Volume Swell %   24    25    24   24    24    25                              % Tensile Retained                                                                             44    47    47   44    41    37                              % Elongation Retained                                                                          38    40    41   36    32    28                              __________________________________________________________________________    Cure Program Variability, Examples 28-34                                                       Example No.                                                                   28   29   30   31   32   33   34                             __________________________________________________________________________    CURE PROGRAM (MINUTES)                                                        Mix Rubber Component                                                                           0    0    0    0    0    0    0                              Add PP then Mix  4    4    4    4    4    4    4                              Dynamic (Mixer) Cure Time                                                                      1    3    3    3    5    5    5                              Roll Mill Time   1    1    1    1    1    1    1                              Static (Oven) Cure Time                                                                        4    0    2    4    0    2    4                              Roll Mill Time   0    0    0    0    0    0    0                              Total Mixer Time 5    7    7    7    9    9    9                              Total Cure Time  5    3    5    7    5    7    9                              PHYSICAL PROPERTIES                                                           Ultimate Tensile (psi/mPa)                                                                     1131/7.8                                                                           1246/8.6                                                                           1265/8.7                                                                           1236/8.5                                                                           1266/8.7                                                                           1300/9.0                                                                           1300/9.0                       Elongation (%)   266  261  260  244  268  284  281                            100% Modulus (psi/mPa)                                                                         705/4.9                                                                            784/5.4                                                                            765/5.3                                                                            790/5.4                                                                            760/5.2                                                                            776/5.3                                                                            793/5.5                        200% Modulus (psi/mPa)                                                                         983/6.8                                                                            1097/7.6                                                                           1085/7.5                                                                           1105/7.6                                                                           1084/7.5                                                                           1087/7.5                                                                           1084/7.5                       Tension Set @ 100% Elong.                                                                      25   25   25   23   25   25   25                             Compression Set (212° F./70 hrs)                                                        77   71   73   69   73   73   70                             ASTM Oil #2, 250° F./70 Hrs                                            Volume Swell %   7    7    6    6    6    7    7                              % Tensile Retained                                                                             50   56   47   60   53   52   54                             % Elongation Retained                                                                          29   38   31   47   40   37   39                             ASTM Oil #3, 250° F./70 Hrs                                            Volume Swell %   24   25   24   23   23   24   25                             % Tensile Retained                                                                             44   48   49   49   38   46   47                             % Elongation Retained                                                                          39   46   48   49   32   44   42                             __________________________________________________________________________     -- not measured                                                          

The data presented in Table VII demonstrate that a combination ofdynamic curing and static curing provides results in terms of physicalproperties which are generally equivalent to those obtained with dynamiccuring, e.g. Example 18 versus Example 25. The reduction in mixer timecorresponds to a reduction in cost of the resulting cured blend.

EXAMPLES 35-38 Effect of CPE Feedstock Melt Index Upon PhysicalProperties

By duplicating the composition of Example 5 save for the type of CPE,samples are prepared for physical property testing. All of the CPE'shave a chemically combined chlorine content of 36 percent by weight ofpolymer and a heat of fusion of 0.2 calories per gram. They differprimarily in terms of the melt index of the feedstock from which theyare prepared. Melt index is determined in accordance with ASTM D-1238,condition 190/2.16. In Example 35, the CPE is prepared from a 0.1decigram per minute feedstock and is commercially available from The DowChemical Company under the trade designation TYRIN™ 3615. In Example 36,the CPE is prepared from a 0.3 decigram per minute feedstock and iscommercially available from The Dow Chemical Company under the tradedesignation TYRIN™ CM0136. In Example 37, the CPE is prepared from a 1.0decigram per minute feedstock and is commercially available from The DowChemical Company under the trade designation TYRIN™ CM552. In Example38, the CPE is prepared from a 6.0 decigram per minute feedstock and iscommercially available from The Dow Chemical Company under the tradedesignation TYRIN™ CM0636. The physical property data are summarized inTable VIII.

                  TABLE VIII                                                      ______________________________________                                        CPE FEEDSTOCK MELT INDEX VARIATION                                            Process/Physical                                                              Property      Physical Property Measured Value                                (Unit of Measure)                                                                           Ex. 35   Ex. 36   Ex. 37 Ex. 38                                 ______________________________________                                        Specific Gravity                                                                            1.11     1.11     1.11   1.11                                   Hardness, Shore A                                                                           83       86       85     87                                     Ultimate Tensile                                                                            1330/9.2 1105/7.6 1015/7.0                                                                             812/5.6                                (psi/MPa)                                                                     Elongation (%)                                                                              292      290      266    167                                    100% Modulus  689/4.8  710/4.9  695/4.8                                                                              720/5.0                                (psi/MPa)                                                                     200% Modulus  1002/6.9 989/6.8  904/6.2                                                                              --                                     (psi/MPa)                                                                     Tension Set @ 100%                                                                          25       25       29     30                                     Elong.                                                                        Compression Set                                                                             69       73       80     77                                     212° F./70 Hours                                                       Low Temperature                                                                             -37      -32      -33    -35                                    Brittleness °C.                                                        ASTM Oil 2, 250° F./70                                                 Hrs                                                                           Volume Swell (%)                                                                            7        4        16     11                                     % Tensile Retained                                                                          53       62       46     46                                     % Elong. Retained                                                                           49       45       45     44                                     ASTM Oil 3, 250° F./70                                                 Hrs                                                                           Volume Swell (%)                                                                            27       21       38     24                                     % Tensile Retained                                                                          43       52       35     46                                     % Elong. Retained                                                                           42       44       33     44                                     ______________________________________                                         -- not measured                                                          

The data presented in Table VIII highlight three benefits fromdecreasing the feedstock melt index. First, the tensile strength of thevulcanized blend increases. Second, the tensile set and compression setof the vulcanized blend decrease. Finally, the resistance to oilsincreases. Similar results are obtained with other compounds which arerepresentative of the present invention.

EXAMPLES 39-42 AND COMPARATIVE EXAMPLE G Effect of Thermoplastic PolymerAmount Upon Physical Properties

Using the composition of Example 5, save for the amount ofpolypropylene, samples are prepared for physical property testing. TableIX includes the amount of polypropylene in parts per hundred parts ofchlorinated polyethylene as well as in terms of percent by weight ofcomposition. Table IX also displays data from the physical propertytesting.

                                      TABLE IX                                    __________________________________________________________________________    Effect of Varying the Amount of Thermoplastic Polymer Amount                  Process/Physical Property                                                                   Physical Property Measured Value                                (Unit of Measure)                                                                           Ex. 39                                                                            Ex. 40                                                                            Ex. 41                                                                             Ex. 42                                                                             Comp Ex. g                                    __________________________________________________________________________    Polypropylene Fraction                                                        Parts/100 parts CPE                                                                         12  41  78   126  191                                           % of Composition Wt.                                                                        4.8 14.4                                                                              24.2 34.0 43.9                                          PHYSICAL PROPERTY:                                                            Specific Gravity                                                                            1.16                                                                              1.13                                                                              1.09 1.06 1.04                                          Hardness, Shore A                                                                           43  72  89   94   98                                            Elongation (%)                                                                              303 310 272  247  293                                           Tension Set @ 100% Elong.                                                                   10  20  35   45   50                                            Ultimate Tensile (psi/MPa)                                                                  786/5.4                                                                           965/6.6                                                                           1248/8.6                                                                           1451/10.0                                                                          1796/12.4                                     100% Modulus (psi/MPa)                                                                      227/1.6                                                                           442/3.0                                                                           823/5.7                                                                            1132/7.8                                                                           1496/10.3                                     ASTM Oil 2, 250° F./70 Hrs                                             Volume Swell (%)                                                                            4   6   6    7    7                                             % Tensile Retained                                                                          77  61  64   83   96                                            % Elong. Retained                                                                           63  39  37   53   53                                            __________________________________________________________________________

A review of the data presented in Table IX show that thermoplasticelastomer materials result when polypropylene comprises from about fiveto about thirty-five percent of the composition weight (twelve to 126parts per hundred parts of chlorinated polyethylene). When thepolypropylene fraction increases to about forty-four percent of thecomposition weight (191 parts per hundred parts of chlorinatedpolyethylene), the tension set at 100% elongation reaches 50. As notedherein, a value of 50 or greater generally indicates a materialunsuitable for use as an elastomer. As such, an upper limit on theamount of this type of polypropylene falls within the range of 126 to191 parts per hundred parts of chlorinated polyethylene. When thepolypropylene fraction falls below about five percent (about twelveparts per hundred parts of chlorinated polyethylene), the dynamicallyvulcanized composition exhibits characteristics of a thermoplasticelastomer notwithstanding some mold shrinkage when compression moldedsamples are prepared.

Similar results are expected from other compositions representative ofthe present invention. Although upper and lower limits on the amount ofthermoplastic polymer may vary with the type of polymer, satisfactoryresults are readily attainable without undue experimentation.

What is claimed is:
 1. A thermoplastic elastomeric composition having atension set value, at 100% elongation, or less than about 50% comprisinga blend of one hundred parts by weight of an amorphous chlorinatedpolyethylene resin, from about twelve to about one hundred fifty partsby weight of a crystalline thermoplastic polyolefin resin, andplasticizing material in an amount of from about five to about onehundred fifty parts by weight, and a vulcanizing package comprising aninorganic base and 2,5-dimercapto-1,3,4-thiadiazole or a derivativethereof, the composition being processable in an internal mixer toprovide a product which forms an essentially continuous sheet followingtransfer, with the resin components in a heat-plastified state, to therotating rolls of a rubber mill.
 2. The composition of claim 1 whereinthe product is prepared by dynamic vulcanization or by a combination ofdynamic vulcanization and static curing in the presence of a vulcanizingpackage comprising an inorganic base and (a)2,5-dimercapto-1,3,4-thiadiazole and an activator material or (b) aderivative of 2,5-dimercapto-1,3,4-thiadiazole.
 3. The composition ofclaim 1 further comprising carbon black in an amount of from about 0 toabout forty parts by weight per one hundred parts by weight ofchlorinated polyethylene.
 4. The composition of claim 1 furthercomprising heat and ultraviolet light stabilizers for said chlorinatedpolyethylene.
 5. The composition of claim 1 wherein the plasticizingmaterial is selected from the group consisting of trimellitate esters,phthalate esters, aromatic oils, and polyesters of dicarboxylic acid. 6.The composition of claim 1 wherein the plasticizing material is trioctyltrimellitate.
 7. The composition of claim 1 wherein the amount ofplasticizing material is from about thirty to about two hundred fiftyparts by weight per one hundred parts by weight of chlorinatedpolyethylene resin present in the blend.
 8. The composition of claim 1wherein the crystalline thermoplastic polymer is selected from the groupconsisting of low density polyethylene, medium density polyethylene,high density polyethylene, polypropylene and block copolymers ofethylene and propylene.
 9. The composition of claim 1 wherein thecrystalline thermoplastic polymer is high density polyethylene orpolypropylene.
 10. The composition of claim 1 wherein an inorganic baseis selected from the group consisting of basic metal oxides andhydroxides and their salts with weak acids.
 11. The composition of claim1 wherein an inorganic base is selected from the group consisting ofmagnesium oxide, magnesium hydroxide, barium carbonate, barium oxide,calcium oxide, and calcium hydroxide.
 12. The composition of claim 1wherein an inorganic base is magnesium oxide or magnesium hydroxide. 13.The composition of claim 1 wherein the vulcanizing package comprises aninorganic base, 2,5-dimercapto-1,3,4-thiadiazole and an activatormaterial selected from (1) amines having a boiling point above about110° C. and a pK value below about 4.5; (2) salts of amines having pKvalues below about 4.5 with acids having pK values above about 2.0; (3)quaternary ammonium hydroxides and their salts with acids having pKvalues above about 2.0; (4) diphenyl- and ditolyl-guanidines; and (5)the condensation products of aniline and at least one mono-aldehydecontaining one to seven carbon atoms in combination with at least anequal amount of an inorganic base.
 14. The composition of claim 1wherein the vulcanizing package comprises a derivative of2,5-dimercapto-1,3,4-thiadiazole selected from the group consisting of:##STR4## wherein X is a substituent selected from hydrogen, --CRR'OH,--(CH₂ --CH--O)_(n) H, ##STR5## where m is an integer of from 2 to 10;where n is an integer from 1 to 5, R and R' are selected from hydrogen,alkyl groups containing 1-8 carbon atoms, and aryl, alkaryl or aralkylgroups containing 6 to 8 carbon atoms; R² is selected from alkyl groupscontaining 1-17 carbon atoms, aryl groups containing one to two rings,alkaryl groups containing 7-14 carbon atoms, aralkyl groups containing7-8 carbon atoms and cyclohexyl groups; R³ is an alkyl group containing1-8 carbon atoms; X' is the same as X with the exception of hydrogen; mis an integer from 1 to 10; and Y is selected from zinc, lead, ##STR6##where R⁴ is selected from alkylene and alkenylene groups containing 1-8carbon atoms and cycloalkylene, arylene or alkarylene groups containing6-8 carbon atoms; z is 0 or 1; and R⁵ is an alkylene group containing2-8 carbon atoms, or a phenylene, methylphenylene ormethylenediphenylene group.
 15. The composition of claim 1 wherein thecrystalline thermoplastic polymer is a solid, high molecular weight,resinous plastic material made by polymerizing olefins selected from thegroup consisting of ethylene, propylene, butene-1, pentene-1 and4-methylpentene.
 16. A thermoplastic elastomeric composition having atension set value, at 100% elongation, of less than about 50% comprisinga blend of one hundred parts by weight of an amorphous chlorinatedpolyethylene resin, from about twelve to about one hundred fifty partsby weight of a crystalline thermoplastic polyolefin resin, andplasticizing material in an amount of from about five to about onehundred fifty parts by weight, and a vulcanizing package comprising MgO,Mg(OH)₂, or both, and 2,5-dimercapto-1,3,4-thiadiazole, the compositionbeing processable in an internal mixer to provide a product which formsan essentially continuous sheet following transfer, with the resincomponents in a heat-plastified state, to the rotating rolls of a rubbermill.
 17. The composition of claim 16 further comprising an activatormaterial selected from the group consisting of tetrabutylammoniumbromide, and the reaction product of aniline and butyraldehyde.
 18. Thecomposition of claim 17 wherein the plasticizing material is trioctyltrimellitate.
 19. A thermoplastic elastomeric composition having atension set value, at 100% elongation, of less than about 50% comprisinga blend of one hundred parts by weight of an amorphous chlorinatedpolyethylene resin, from about twelve to about one hundred fifty partsby weight of a crystalline thermoplastic polyolefin resin, andplasticizing material in an amount of from about five to about onehundred fifty parts by weight, and a vulcanizing package comprising aninorganic base and 2,5-dimercapto-1,3,4-thiadiazole or a derivativethereof and an activator material, the composition being processable inan internal mixer to provide a product which forms an essentiallycontinuous sheet following transfer, with the resin components in aheat-plastified state, to the rotating rolls of a rubber mill.
 20. Thecomposition of claim 19 wherein the plasticizing material is trioctyltrimellitate.